1. Field of the Invention
This invention relates to voltage regulator circuits in general and more particularly to low cost stable voltage regulators controlled by a constant current generator having a voltage regulator device and having a low voltage inhibit circuit.
2. Description of the Related Art
It is well known that microcomputers operating from regulated power supplies must be inhibited during both the power-up phase and also in the event that the DC power to the regulated power supply is interrupted or drops below a predetermined level. U.S. Pat. No. 5,313,112 issued on May 17, 1994 to Macks entitled "Low Voltage Inhibiting Circuit For A Microcomputer" and is incorporated herein by reference, sought to find a low cost solution to achieving the desired functions. This patent required separate voltage regulating circuits. One circuit to provide the regulated supply voltage and another circuit to use as a comparison reference for the power on reset and the low voltage inhibit functions.
In U.S. Pat. No. 5,760,625 issued on Jan. 2, 1998 to Macks entitled "Low Cost Microcomputer Power Supply With Power On Reset And Low Voltage Inhibit Functionality" that is incorporated herein by reference, describes a five volt regulator with a reset circuit. This circuit is not robust to the swings in the power feed potential. In automotive applications the power feed is the vehicle battery which is subject to large variations in potential from 3 to 18 volts.